Process for the treatment of petroleum distillates



Patented Feb. 25, 1941 PROCESS FOR THE TREATMENT OF PETROLEUM DISTILLATES Joseph H. Balthis, Jr., Wilmington, Del., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware Application September 21, 1938, Serial No. 230,980

8 Claims.

This invention relates to a process and apparatus for producing at least one of the members of the group consisting of benzol, toluol, xylol, and aromatic naphthas from petroleum distillates containing a high portion of such hydrocarbons.

Petroleum distillates intended for consumption as gasoline have been treated with sulfuric acid for many years with the object of removing objectionable sulfur compounds and unstable unsaturated hydrocarbons. Petroleum distillate also have been treated by bringing them in contact at elevated temperatures with catalytically active clay with the object of effecting a reduction in the objectionable unsaturated hydrocarbons. However, prior to this invention it has not been known how compounds such as benzol, toluol, xylol, and aromatic naphthas could be separated under normal commercially feasible conditions from a petroleum distillate containing them so as to obtain said compounds in commercially pure form.

This invention has as its object the recovery of benzol, toluol, xylol, and aromatic naphthas from petroleum distillates which contain such hydrocarbons. A further object is a process which enables the recovery of any one or all of these hydrocarbons in good yield and in pure condition. A still further object is a method of effecting the extraction of acidic ingredients and the breaking of water emulsions sometimes found in the overhead distillate and reflux of stills in which acid-treated hydrocarbons are being rectified. Another object is to provide apparatus for accomplishing the foregoing objects. Other objects will appear hereinafter.

These objects are accomplished by the following invention which comprises subjecting the petroleum distillate to the polymerizing action of clay, separating the polymers thereby formed,

further refining the clay-treated material with sulfuric acid, and, finally, rectifying to free same of-polymers and undesirable constituents. Durin'g'the final rectification further purification is effected at option by subjecting the column reflux and drawofl to continuous mechanical agitation with aqueous alkali.

The accompanying drawing is a flow sheet diagrammatically illustrating an embodiment of this invention.

As starting materials in this invention there is used a highly aromatic petroleum distillate which is defined as a light petroleum fraction consisting predominately of aromatic hydrocarbons. This fraction usually/contains more or less unsatu-,

rated hydrocarbons and is preferably relatively free from parailins and naphthenes. In general such a fraction will boil between about 60 C. and about 220 C. The term aromatic naphtha," as designating one of the desirable products, denotes any mixture of monoor poly-alkylated benzenes which has a true boiling point range falling within the limits of about 144 C and about 218 C. Petroleum oil is delivered into a work tank where it is mixed with other oil fractions subsequently to be described. The mixture of oils is preheated to 325 to 385 C., high-boiling liquid constituents are separated in an evaporator, and

the temperature of the vaporized portion is raised to 460 to 490 C. in drying tubes and, finally, to 690 to 710 C. in tubes in which cracking occurs. The reaction products pass by way of soaking tubes maintained at 690 to 710 C to an arrestor in which the temperature is lowered by quenching with oil. Heavy fuel oil and tar are separated in a flash tower, oil with a boiling range between distillate and fuel oil is separated in a fractionating tower, and these fractionating tower bottoms are returned to the work tank and recycled. The eiliuent vapors from the fractionator pass by way of a condenser into a gas-liquid separator from 2 which the highly aromatic distillate is withdrawn to storage tanks.

A marked increase in the yield of aromatic and gaseous oleflnic hydrocarbons can be attained by recracking a portion of the gas from the separator. This gas is separated into fractions by a series of steps involving compression, liquefaction, and rectification. The fractions consists of 1) hydrogen-methane, (2) ethylene, (3) ethane and C: and C4 hydrocarbons, and (4) C5 and higher hydrocarbons. "Fraction (4) is returned to the work tank for recycling. Fraction (3) is fed into preheating tubes in which the temperature is raised to 650 to 700 C., and then into cracking coils at 760 to 790 C. After lowering the temperature in an arrestor, the cracked material is added to that issuing from the arrestor of the oil cracking unit. The combined vapors then pass into the flash tower and though the cracking and product separation cycle which has been described. Distillate prepared in this manner contains an unusually high percentage of aromatic hydrocarbons which can be readily recovered in pure form by the processes of this invention. In order to properly illustrate this invention the following detailed description is given herein. This description is not to be considered as limiting said invention in any respect.

Referring to the drawing, a highly aromatic petroleum distillate, such as produced by the s PATENT OFFICE above described process, is introduced via conduit 2 into the charge tank 4. The raw distillate is withdrawn from the charge tank via conduit 6 and is pumped via pump means I through heating coil l0, where the temperature is raised to between 250 and 350 C.. and thence into the clay chamber l2 which contains catalytically active clay and is maintained at a temperature of about 250 to about 350 C.

The distillate from the clay chamber l2 passes via conduit [4 through the pressure release valve l6 where the pressure is adjusted to about 30 lbs. per sq. in. The temperature of the oil is then adjusted from about 300 C. to about 150-250 C. by passing said oil either through the cooler l8 or heater 20, if heating or cooling be needed. The distillate is then introduced into fractionating tower 22 via conduit 24.

In the fractlonating tower 22 the polymers and high boiling products from the clay treatment are separated as a liquid traction and withdrawn from the bottom of said tower via conduit 28. These may be cooled in cooler 28 and stored in a suitable storage 30. The overhead vapors of stripped distillate are withdrawn from the top of the fractionating column 22 via conduit 32, cooled in the cooler 34 so as to condense the same, and then passed into receiver 36. The stripped distillate is withdrawn from the bottom of receiver 30 via conduit 38, where it is admixed with suli'urlc acid, introduced via conduit 40 into conduit 30, sulfuric acid being withdrawn as needed from a sulfuric acid storage 42.

The mixture of distillate and sulfuric acid is cooled, if desired, by the cooler 44 and intimately mixed in contactor 45. The distillate and spent acid pass directly or byway of cooler 46 into the settling tank 41. Sludge acid is withdrawn from the base of this settling tank via conduit 48 and the sour distillate is withdrawn from the top of the settling tank via conduit 50, and introduced into the neutralizing mixer 52. Aqueous caustic soda solution is also introduced into said neutralizing mixture from the caustic storage 54 via conduit 56. The resulting mixture from the neutralizing mixer 52 is withdrawn via conduit 58 and introduced into separator 60, where the spent caustic settles to the base of said separator, making possible its removal via conduit 62. The neutralized distillate is then withdrawn from separator 80 and introduced into the distillate storage 64, prior to its being charged into the pot 66 of the batch still.

The batch still consists of the pct 66, the rectitying column 68, and the backwards return condenser 10. During rectification the overhead vapors from the rectifying column 00 are condensed in the backwards return condenser 10, and withdrawn via conduit 12. The condensate is further cooled by cooler 14 and forced by pump 16 into the caustic agitator 18, where it is admixed with an aqueous alkaline solution containing about 30% caustic soda introduced via conduit 80. The mixing action is accomplished by driving the stirrer 82 with a variable speed motor 84. The condensate with mechanically entrained alkali then passes by way of conduits 86 or 80 into the caustic settling tank 90, where the aqueous alkali settles from the oil condensate and fiows back to the caustic agitator 18 via conduits 88 or 86. Spent caustic may be withdrawn from the caustic settler via conduit 92.

The refined condensate 'then passes through the cylinder 94, where the last traces of the aqueous caustic solution is removed by settling. This cylinder 94 is preierably constructed of a transparent material like glass so as to permit the visual observation of the thoroughness of settling. A portion or the condensate is withdrawn as product by means of conduit 00 and the remainder is returned via conduit 06 to the top of the rectifying column 80 to be used as reflux therein. when the product in conduit 00 is slightly corrosive it may be treated with an aqueous sodium hypochlorite solution introduced through conduit I00 and the mixture allowed to stand in separating tank I02 for several hours. The refined aromatics may be removed from the tanks via conduit I04.

The above description represents one detailed method and apparatus for carrying out the invention described herein. This method and apparatus, however, may be varied in many respects, as will be discussed hereinafter, without departing from the spirit or scope of the invention.

The examples which follow are also specific illustrations of this invention. These examples, like the foregoing description, are not intended to limit the invention in any respect. Examples 2, 3, and 4 describe the refining operations 01' this invention starting with raw distillate. The remaining examples describe modifications in the clay and acid-treating steps, and illustrate some of the variations which can be made in carrying out the processes of the invention. Unless otherwise stated, yields are expressed in volumn per cent and specific gravities at /60 F.

Example 1 Raw distillate with a true boiling point range of 38 to above 218' C., a specific gravity of 0.8524, and produced as described by cracking petroleum oil at 690 to 710 C., was iractionally Distillate of fraction B, Example 1, was preheated to 310 C. and passed in the liquid phase at 600 pounds pressure through a bed of Attapulgus 20-60 mesh clay which had been previously air-dried but not burned. External heat was applied to the clay chamber, as necessary, to maintain an average temperature of about 330 C. The distillate was discharged at atmospheric pressure. and cooled. The exothermic polymerization was accompanied by a shrinkage in volumn, and a 98.7% yield of dark-colored product with a specific gravity oi 0.8676 was obtained.

Polymers were stripped from the clay treated distillate in a continuous distillation column, giving a 90.6% yield (based upon iraction B, Example 1) of colorless distillate similar in boiling range to the starting material. The specific gravities oi the distillate and the higher boiling polymers were, respectively, 0.8576 and 0.9698.

Three hundred and sixty-one pounds of the stripped distillate was placed in a steel tank equippedwith a motor driven agitator, a jacket for control of temperature by means of dry ice and acetone, and a conical bottom section fitted with a valve. The oil was stirred with 15.8 Pounds of 96% sulfuric acid for ten minutes at approximately 5 C. After settling for thirty-five minutes, 132 pounds of spent acid was separated, and the oil was stirred for ten minutes at 4:2" C. with 15.1 pounds of 96% acid. Forty-three minutes after the cessation of stirring, 15.3 pounds'of,

' sludge acid had been withdrawn. A final wash allowed to settle for forty hours.

was given with 23.4 pounds of 96% acid at 6i4 C. for ten minutes, and 36.6 pounds of sludge was separated after settling for 49 minutes. The sour distillate was stirred at once with 14.0 pounds of 30% caustic soda solution for five minutes and Three hundred forty-eight and one-half pounds of distillate and 13.8 pounds of spent caustic were recovered.

The neutralized oil was combined with another lot which had been treated identically and the composite weighing 625 lbs. was rectified in a 6"x30' packed column, the pot of which was heated indirectly by high pressure steam. Nine pounds of anhydrous sodium carbonate was added to the still pot with the charge.

The yields of the rectified fractions and their more significant properties follow:

thirty minute periods of contacting, and the spent acid was withdrawn before adding a fresh portion. The sour distillate was agitated for three hours with 10% by volume of 20 B. caustic soda and allowed to stand for 48 hours before separation of spent caustic. Eighty-seven per cent of the original oil was recovered. I

Upon fractional distillation, an 82.5% yield of colorless oil boiling from 792 to 2l4.4 C. was obtained. Examination of small fractions indicated that when small cuts of intermediate boiling point were isolated, the major part of the material fulfilled specifications for high purity benzol, toluol, xylol, and aromatic naphtha.

Example 4 Boiling Yield Fmezm Barrett Corrosive a pe Fraction 53%; in point, at 1pm? C. pounds a 25/25 number perstrlp 1 Benzol 79. -95. 5 254. 8 4. 47 0.8723 0-1 None. 2 T011101 95.5- 134 193.0 0.8591 0-1 D0. 3 xylol 134-144 73. 4 0. 8559 3 Slight.

Pot residue Above 144 87. 9 0.8987

It will be observed that fractions 1, 2, and 3 approach the properties of pure benzol, toluol, and 10 xylol. Since it is impossible to rectify a mixture of materials so that 100% of each constituent is secured in a pure condition, small fractions of intermediate boiling point are normally isolated for refractionation. When such cuts were isolated in this distillation, it was apparent that the main fractions consisted of benzol, toluol, and xylol of high purity. This is proven by the resuits of tests such as those which follow:

Boiling Freezing Sp. gr. ggs gggfig; Fraction point, point, at h number strip 1 BenzoL. 80.2 5.41 0.8731 0 None. 2 Toluolm 110.4 0.8617 0-1 Do. 3 Xylol 134-144 0.8559 3 Slight.

Example 3 Petroleum gas oil was cracked at 690 to 710 C. with recycling of the ethaneCa--C4 hydrocarbon fraction as described, and the raw distillate therefrom was contacted with Floridintype clay at 600 lbs. pressure and 219 C. The raw distillate had a, true boiling point range of -40 to 225 C, and a gravity of 0.8453. The &

the polymers and distillate were, respectively, 1.020 and 0.8565. Before stripping, the dark col ored oil had a gravity of 0.910.

Ten gallons of the above distillate which boiled from 144 to 218 C. was treated in a unit designed to simulate commercial operation; that is, acid contacting, sludge separation, and neutralization were performed continuously. Eight and seventy-eight hundredths volume per cent of 96% acid was applied with an over-all treating loss of 9.55%. Polymers were removed in a continuous still at reduced pressure, and aromatic naphtha boiling from 142 to 218 C. was recovered in 79.5% yield based upon the material treated.

The aromatic naphtha was found to corrode a clean copper strip when heated in contact therewith. This corrosiveness was reduced by mixing the naphtha for two hours with 20% by volume of aqueous sodium hypochlorite. The hypochlorite solution contained 10.4 grams of available chlorine and 1.52 grams of free sodium hydroxide per liter.

Example 5 Raw cracked distillate, with a specific gravity of 0.8448 and boiling from -38 to 160 C. but mainly from 80 to 144 C., was preheated and subjected to the action of A-ttapulgus-type clay at 800 pounds pressure and 332 C.. The clay was 20-60 mesh and 33.5 lbs. per cu. ft. in density.

The usual exothermic polymerization resulted in a 96.9% yield of dark-colored product with a gravity of 0.8612. Polymers separated by distillation had a gravity of 0.9516 and the stripped distillate, boiling from 31.4 to 164.01 C. and with a gravity of 0.8545, was recovered in 85.6% yield.

Two hundred and fifty cubic centimeters of a fraction of the above distillate, said fraction boiling from 144 to 218 C., was subjected to three ten-minute periods of agitation with a total of l'brty gallons of highly aromatic petroleum distillate boiling approximately from 78 to 146' C., which had been clay treated and stripped of polymers as described in Example 2, was treated in a pilot plant designed to simulate a continuous commercial unit. The distillate was continuously contacted with 7.12 volume per cent of 96% sulfuric acid in small high-speed Stratford-type comtactors for 2.4 minutes. The mixture of acid and oil flowed through a water cooler into a settling tank where the spent acid was continuously removed, and thence into a tank where neutralization was concurrently effected with 2 volume per cent of 30 36. caustic soda. Treating losses were 1.68, 2.73, and 2.39 volume per cent, respectively, for sludge absorption, change in gravity, and neutralization. The temperature ranged from 17 to 54 C. during acid contact.

The neutralized distillate was stripped of poly mer in a continuous column and recovered in 81.33% yield, based upon clay-treated distillate. The specific gravities of the distillate and the polymers were 0.8681 and 0.8894, respectively.

By redistillation the distillate was separated into fractions having the properties shown below. These fractions meet commercial requirements for non-corroslve-chemically pure benzol, etc.

temperatures between 250 and 350 C. and under a pressure sufiicient to keep the reactants in the liquid phase, which ordinarilly need not exceed about 600 lbs. per sq. in. It is preferred that the raw distillate remain in contact with the clay forsufiicient length of time to effect the maximum practical polymerization of the more unstable unsatm-ates. The clay-treating step herein described differs from the step inually used in treating gsolines as it, is preferred here to operate at higher temperatures. Variation in temperature may be compensated by appropriate variation in time of contact but temperatures above 350' C, are not recommended for excess carbonimtion of the charge and clogging of the interspaccs of the clay may occur.

The polymers formed by the clay-treating step should be stripped from the distillate before subjecting same to the treatment with acid. This stripping is carried out preferably in a continuous still and immediately upon discharge of the hot distillate from the clay chamber. However, while such procedure is preferable, it is not 11 and a batch still may be used.

In the sulfuric acid-treating step it is desirable to contact the clay-treated distillate with a concentrated sulfuric acid, preferably of the strength of about 75 to about 97%. The contact between the concentrated sulfuric acid and distillate may be procuredin a batch agitator, as indicated above, or by continuous contacting means, it being merely necessary to maintain an intimate contact for the minimum length of time required to elect the desired purification. The concentrated sulfuric acid should be added at a temperature of 30 C. or below, and in an amount varying from about 0.3 to about 7% by volume of the charge. -This distillate may be treated one or more times.

Boning di s fl l l a t Memng Sp. gr. at add dict Fmmn P included 2 l5.5/i5.5 C. w-h upon coptherein numb pcstrip B00101. in? .46. 25 5. 01 0. 88% 0-1 NOM- Tolnol- 110. 4 33. 0. 867 2-! Do. Xylol 134-144 13. 12 0. 882 ML These processes can be carried out to yield products of very high purity ordinarily designated as "non-corrosive nitration-pure aromatics, or less pure hydrocarbons commonly described as chemically-pure, or products in any permissible lesser state of purity. Tests such as freeidng point, specific gravity, acid wash, iodine number, sulfur content, and copper-strip corrosion, which are familiar to those versed in the art, are useful in determining purity.

The clay-treating process is not limited by the procedures described, and any variation, familiar or obvious to those skilled in the art, may be made without departing from this invention. For example, the use of Attapulgus clay is described but any type of fuller's earth or material of equivalent catalytic activity can be substituted therefor. Likewise the clay-treatment may be conducted in either the liquid or vapor phase, at atmospheric or higher pressures, and at any temperature at which polymerization of the unsaturates present is obtained. The treated or stripped oil at option may be recycled to the treating zone, and the clay may be reactivated by known processes.

It is usually desirable that the raw distillate be contacted with the catalytically active clay at The number of times that the distillate is contacted with sulfuric acid depends upon various factors such as the character and amount 01. unsaturation of the charge, the emciency of the contact. etc. Likewise the length of time of contact between the sulfuric acid and the distillate depends upon such factors. If the distillate is treated more than once with sulfuric acid, the spent acid should be withdrawn between each treatment step and before adding the fresh acid. In any event the acid treatment is continued until the remaining unsaturates have been polymerized. After the acid treatment the sour oil should be promptly neutralized.

As pointed out, the acid refining process can be conducted continuously as well as batch-wise. In continuous operation it is preferred to use high speed contactors and relatively short time of contact; for example, a distillate which required agitation for three ten-minute periods in a batch agitator was refined to comparable quality in 2.4 minutes by the same volume of acid in a continuous unit equipped with small highspeed Stratford-type contactors. With these shorter times of contact temperature control is of less importance, and treating temperatures ranging from 0 to 60 C. are satisfactory.

The acid-treated and neutralized "distillate is rectified to sep a e p y e s a d cki in sulfur compounds. The aromatic fractions therefrom occasionally contain alkali-soluble sulfur compounds and emulsified water, the presence of which is attributed to the thermal decomposition of sulfur compounds surviving or introduced in the acid treatment. The removal of both the acidic impurities and the water can be accomplished by adding gaseous ammonia during rectification or by scrubbing the overhead column vapors countercurrently with aqueous caustic soda. Their formation may be lessened by steam distillation prior to rectification or by rectification at reduced pressure. In the preferred embodiment, however, acidic compounds and water are removed by continuously agitating the column reflux and drawoff with aqueous alkali. Liquid overhead from the column flows by gravity or force through a chamber in which it is mechanically agitated with aqueous caustic soda, and thence through a chamber in which mechanically entrained caustic soda settles. The alkali flows back into the agitator, and the distillate, after withdrawing that portion desired as product, returns to the head of the rectification column as reflux.

The product consists essentially of aromatic hydrocarbons, but may be contaminated by traces of water and sulfur compounds. As is well known, the water may be separated by drying agents such as sodium hydroxide or anhydrous calcium chloride and the sulfur compounds may be removed or transformed into non-corrosive form by sweetening with hypochlorite solution.

Benzol, toluol, xylol, and aromatic naphthas have a true boiling point range of approximately 80 to 218 C. The successive treatment with clay and sulfuric acid of raw distillate consisting essentially of unsaturated and aromatic hydrocarbons and boiling within this range permits the recovery of practically all of the indicated hydrocarbons in substantially pure form; that is, free from unsaturates. However, the processes of this invention apply equally well to cuts containing only one or more aromatic hydrocarbons together with unsaturates. To illustrate, a raw distillate boiling from 80 to 150 C. can be processed to yield benzol, toluol, and xylol, and a 150 to 218 C. out of raw distillate can be processed separately to aromatic naphtha substantially free from unsaturates.

In the distillates obtained in the oil-cracking operation, the boiling points of the unsaturated hydrocarbons are not always evenly distributed over the entire boiling range of a raw distillate and may be relatively close together.

This invention has the advantage of producing aromatics and a distillate having a composition approximating solvent naphthas in substantially pure form by a relatively simple procedure. Benzol and/or toluol and/or xylol and/or aromatic naphtha can be obtained in any desired state of purity. This result is not obtainable when starting with a highly aromatic petroleum distillate and applying either the clay treatment alone or the acid treatment alone. By the use of sulfuric acid alone, the resulting product is diiiicult to purify. Further, if the raw material is first brought in contact with the sulfuric acid. excess sheat is generated and the reaction is hard to control. The resulting acid sludge is very viscous and diflicult to separate by mere settling means.

y y m nt alone the raw material is only partially purified and the product still contains alarge percentage of oleflnes. From the resulting clay treated material the desired products cannot be obtained in substantially pure form. bymere distillation, 1 V This invention therefore represents a marked advance over the prior processes for by first clay treating .a highly aromatic petroleum distillate and then treating said distillate with sulfuric acid, a product is obtained from which substantially pure benzol and/or toluol and/or xylol and/or aromatic naphtha can be obtained by simple fractionation. I I

It is apparent that many .widely different embodiments of this invention may be made without departing from the spirit and scope thereof and therefore it is not intended to be limited except as indicated in the appended claims.

I claim:

1. A process of producing aromatic hydrocarbons from petroleum distillate containing a high portion of such hydrocarbons which comprises contacting said petroleum distillate with a catalytically active clay at an elevated temperature capable of polymerizing unsaturates contained therein and then treating the clay-treated petroleum distillate with concentrated sulfuric acid.

2. A process of producing aromatic hydrocarbons from petroleum distillate containing a high portion of such hydrocarbons which comprises contacting said petroleum distillate with a catalytically active clay at an elevated temperature capable of polymerizing unsaturates contained therein, at least partially separating the resulting polymers, and then treating the clay-treated petroleum distillate with concentrated sulfuric acid.

3. A process of producing aromatic hydrocarbons from petroleum distillate containing a high portion of such hydrocarbons which comprises contacting said petroleum distillate with a catalytically active clay at an elevated temperature capable of polymerizing unsaturates contained therein, at least partially separating the resulting polymers, then treating the clay-treated petroleum distillate with concentrated sulfuric acid, and distilling the resulting sulfuric acid treated petroleum distillate so as to recover a purified fraction containing the aromatic hydrocarbons.

4. A process of producing aromatic hydrocarbons from petroleum distillate containing a high portion of such hydrocarbons'which comprises contacting said petroleum distillate with a catalytically active clay at an elevated temperature capable of polymerizing unsaturates contained therein, at least partially separating the resulting polymers, and then treating the clay-treated petroleum distillate with concentrated S1119 furic acid, separating the spent acid, neutralizing any acid contained therein, and distilling the resulting mixture so as to recover a purified ing mixture so as to recover a purified fraction containing the aromatic hydrocarbons, withdrawing the overhead liquor in said distilling step prior to its use as reflux, and agitating same with an aqueous alkaline solution, separating said aqueous solution, and returning at least a portion 015 said overheadliquor to the rectifying system for use as reflux therein,

6. A process of producing aromatic hydrocarbons from petroleum distillate containing a high portion of such hydrocarbons which comprises contacting said petroleum distillate with a catalyticallyactive clay at an elevated temperature capable of polymerizing unsaturates contained therein, separating polymers from the resulting mixture, then treating said mixture with suliuric acid in such a manner-as to render easily separable the remaining unsaturates, separating the petroleum fraction from the spent acid, neutralizing and distilling the resulting petroleum fraction to separate and recover aproductcomprising essentially aromatic hydrocarbons.

7. The process in accordance with claim 6 characterized in that the clay treating step is carried out with the highly aromatic petroleum distillate in the liquid phase, at a temperature oi about 250 to about 350 0., and under a pressure suilicient to keep the ,reactantsin the liquid phase. I i

8. A process 0! producing aromatic hydrocarbons from petroleum distillate containing a high portion of such hydrocarbons which comprises contacting said petroleum distillate with a catalytically active clay at an elevated temperature capable oi polymerizing unsaturates contained therein, separating polymers from the resulting mixture, then treating said mixture with suliuric acid in such a manner as to render easily separable the remaining unsaturates, separating the petroleum fraction irom the spent acid, neutralizing and distilling the resulting petroleum fraction to separate and recovers. product comprising essentially aromatic hydrocarbons, and

treating the resulting product with an aqueous 20 sodium hypochlorite solution ior suiiicient length of time to remove anytraces of corrosive substance contained therein.

JOSEPH H. BAL'I'HIS, JR. 

